Cathay Pacific and HK Express passengers can now use their mobiles to check in baggage at the airport.

Using the airlines' apps, passengers can get a printed tag at special channels and drop off their luggage.

The function is only available to people with electronic travel documents who are flying to places where they don't require a visa.

Chris Au Young, the general manager of data analytics at the Airport Authority, said the new bag drop service will save passengers time.

"So if we compare that method with the old method, the old method takes two minutes more. If we don't count any time used for lining up, the entire process is shortened from three minutes to only one," he told the media on Wednesday.

Au Young said the authority hopes to expand the function so it can be used by 80 percent of passengers leaving Hong Kong.